Yanagita Toshihiko, Maruta Toyoaki, Nemoto Takayuki, Uezono Yasuhito, Matsuo Kiyotaka, Satoh Shinya, Yoshikawa Norie, Kanai Tasuku, Kobayashi Hideyuki, Wada Akihiko
Department of Pharmacology, Miyazaki Medical College, University of Miyazaki, Kiyotake, Miyazaki 889-1692, Japan.
Neuropharmacology. 2009 Sep;57(3):311-21. doi: 10.1016/j.neuropharm.2009.05.006. Epub 2009 May 30.
In cultured bovine adrenal chromaffin cells expressing Na(V)1.7 isoform of voltage-dependent Na(+) channels, we have previously reported that lithium chloride (LiCl) inhibits function of Na(+) channels independent of glycogen synthase kinase-3 (GSK-3) (Yanagita et al., 2007). Here, we further examined the effects of chronic lithium treatment on Na(+) channels. LiCl treatment (1-30 mM, > or = 12 h) increased cell surface [(3)H]saxitoxin ([(3)H]STX) binding by approximately 32% without altering the affinity of [(3)H]STX binding. This increase was prevented by cycloheximide and actinomycin D. SB216763 and SB415286 (GSK-3 inhibitors) also increased cell surface [(3)H]STX binding by approximately 31%. Simultaneous treatment with LiCl and SB216763 or SB415286 did not produce an increased effect on [(3)H]STX binding compared with either treatment alone. LiCl increased Na(+) channel alpha-subunit mRNA level by 32% at 24 h. LiCl accelerated alpha-subunit gene transcription by 35% without altering alpha-subunit mRNA stability. In LiCl-treated cells, LiCl inhibited veratridine-induced (22)Na(+) influx as in untreated cells. However, washout of LiCl after chronic treatment enhanced veratridine-induced (22)Na(+) influx, (45)Ca(2+) influx and catecholamine secretion by approximately 30%. Washout of LiCl after 24 h treatment shifted concentration-response curve of veratridine upon (22)Na(+) influx upward, without altering its EC(50) value. Ptychodiscus brevis toxin-3 allosterically enhanced veratridine-induced (22)Na(+) influx by two-fold in untreated and LiCl-treated cells. Whole-cell patch-clamp analysis indicated that I-V curve and steady-state inactivation/activation curves were comparable between untreated and LiCl-treated cells. Thus, GSK-3 inhibition by LiCl up-regulated cell surface Na(V)1.7 via acceleration of alpha-subunit gene transcription, enhancing veratridine-induced Na(+) influx, Ca(2+) influx and catecholamine secretion.
在表达电压依赖性钠通道Na(V)1.7亚型的培养牛肾上腺嗜铬细胞中，我们之前报道过氯化锂（LiCl）抑制钠通道功能且不依赖糖原合酶激酶-3（GSK-3）（柳田等人，2007年）。在此，我们进一步研究了慢性锂处理对钠通道的影响。LiCl处理（1 - 30 mM，≥12小时）使细胞表面[³H]石房蛤毒素（[³H]STX）结合增加约32%，而不改变[³H]STX结合的亲和力。这种增加被放线菌酮和放线菌素D抑制。SB216763和SB415286（GSK-3抑制剂）也使细胞表面[³H]STX结合增加约31%。与单独任何一种处理相比，LiCl与SB216763或SB415286同时处理对[³H]STX结合没有产生增加的效果。LiCl在24小时时使钠通道α亚基mRNA水平增加32%。LiCl使α亚基基因转录加速35%，而不改变α亚基mRNA稳定性。在LiCl处理的细胞中，LiCl如在未处理细胞中一样抑制藜芦碱诱导的²²Na⁺内流。然而，慢性处理后洗脱LiCl增强了藜芦碱诱导的²²Na⁺内流、⁴⁵Ca²⁺内流和儿茶酚胺分泌约30%。24小时处理后洗脱LiCl使藜芦碱对²²Na⁺内流的浓度 - 反应曲线向上移动，而不改变其EC₅₀值。短裸甲藻毒素-3在未处理和LiCl处理的细胞中均使藜芦碱诱导的²²Na⁺内流变构增强两倍。全细胞膜片钳分析表明，未处理和LiCl处理的细胞之间的I - V曲线以及稳态失活/激活曲线具有可比性。因此，LiCl对GSK-3的抑制通过加速α亚基基因转录上调细胞表面Na(V)1.7，增强藜芦碱诱导的Na⁺内流、Ca²⁺内流和儿茶酚胺分泌。
Zotero 插件